The present invention relates to a fuel injector.
A fuel injector that may control several injection orifices separately is described in German Published Patent Application No. 32 28 079. The fuel injector has two valve needles which may each be acted upon with a prestressing force by a spring against a sealing seat. If one valve needle is raised from its sealing seat by a certain prelift, it may strike a stop of the other valve needle and pick up this valve needle as it continues its lift. The two sealing seats of the two valve needles may seal different injection orifices which may be oriented at different angles. However, the configuration may have multiple parts and it may be required to precisely manufacture two sealing seats, which may entail high costs. Furthermore, merely two groups of injection orifices may be controlled separately and a further selection of injection orifices to be opened may not be possible.
A fuel injector for internal combustion engines having a valve needle and an auxiliary needle arranged in a bore of the valve needle is described in German Published Patent Application No. 30 48 304. At its combustion chamber side section, configured as a valve-closure member, the valve needle, together with a valve-seat surface, forms a sealing seat, which separates the injection orifices from a fuel supply. The auxiliary needle, guided in the valve needle, also has a valve-closure member, which cooperates with a second valve-seat surface of the fuel injector. A spring, arranged in the valve needle, pulls the auxiliary needle against the valve needle, toward which, together with a valve-seat surface, it also forms a sealing seat in the valve needle. When the hydraulically operated fuel injector begins to open due to an increase in pressure in the fuel line, the auxiliary needle is pressed from its sealing seat in the valve needle against the sealing seat in the valve body, sealing a group of injection orifices, while another group of injection orifices is opened. If the pressure further increases, the valve needle is raised from its sealing seat, and after a certain lift picks up the auxiliary needle, which strikes a stop of the valve needle. All injection orifices may then be opened. Consequently, a total of three precisely manufactured sealing seats may be required. Also, with this conventional fuel injector, merely two groups of injection orifices may be controlled separately.
A fuel injector having two valve needles, in order to open injection orifices in two groups, is described German Published Patent Application No. 31 20 044. Here one valve needle is guided inside the other valve needle, which is configured as a hollow needle. This valve needle, configured as a hollow needle, has injection orifices at its end on the combustion chamber side. The manufacture of the hollow needle may be very complex, because the hollow needle also has injection orifices, and therefore one component may combine two functions, which may require a precise manufacture of the component.
A fuel injector according to an example embodiment of the present invention may provide a cost-effective, and with regard to manufacturing engineering an easily implementable, method of controlling the injection orifices to be opened, since not only may the injection orifices not require another precisely manufactured sealing seat in order to be opened separately, but also the injection orifices, assigned to a valve section, may be opened independently if the respective heating element of the valve section is controlled separately from the valve-closure member. At a maximum, all injection orifices may thus be selected separately if all injection orifices are assigned a respective valve section and the respective heating elements are controllable separately from one another. As soon as the valve-closure member opens, only the injection orifices not covered by their valve sections may inject fuel.
In particular, the distribution of fuel in the jet pattern of the fuel injector may be influenced by the selection of the injection orifices.
At least the valve section of the disk element may be made of bimetal and the lamination of the bimetal may be configured so that the valve section clears the injection orifices when heated.
Alternatively, the valve section of the disk element may be made of bimetal and the lamination of the bimetal may be configured so that the valve sections of the disk element cover the injection orifices when heated.
In an example embodiment at least the valve section of the disk element is made of a shape memory alloy, in particular a shape memory alloy having a two-way effect.
The heating elements may include resistance wires arranged on the valve sections.
At a maximum, all valve sections of the disk element may be separately selected and opened, if a separate control line is provided for each of the resistance wires.
The valve-seat member or the injection orifice plate may have a second hole circle of injection orifices, arranged radially outside of the first hole circle, and correspondingly shaped valve sections of the disk element may be assigned to the injection orifices of the second hole circle.
The injection orifices may have different injection angles, orifice diameters, and axial lengths.